The present invention relates to vacuum blasting, and more particularly, to a blast head for a sealed waste transfer system for vacuum-blasting machines using recyclable abrasives.
As will be appreciated by those skilled in the art, vacuum blasting refers to an improved technology for cleaning and preparing surfaces by blasting the surface with abrasive particles entrained in a relatively high velocity air stream. In vacuum blasting, a small hood surrounds the blasting nozzle, and a vacuum port within the hood, adjacent the nozzle, sucks up the abrasive particles and debris loosened from the surface being blasted. This abrasive particle and debris mixture passes through a hose to a separator, where the debris is separated from the abrasive particles. The separated debris is deposited in a closed waste chamber, which is maintained below atmospheric pressure during the blasting operation. Abrasive particles separated from the debris are returned to a hopper and used again in the blasting operation. Vacuum-blasting machines provide closed-system blasting by making the blast head in effect a small containment structure. Coating and/or corrosion materials removed from the surface being treated and spent abrasive particles are deposited in a closed waste chamber. In operation, the system is virtually dust free and, therefore, relatively safe for the operator and the environment, even when used to blast surfaces covered with potentially hazardous materials, such as lead and radioactive contaminants.
Although the blast heads for such vacuum-blasting systems are generally satisfactory for cleaning large surfaces, they are less than satisfactory for cleaning the sides of bolts, nuts and other elements that project from larger surfaces.